The relative cardiac effects of five different experimental models of cerebral infarction in cats will be compared with one another and with appropriate sham-operated control animals; the effects to be determined are the following: the kinds and the extent of myocardial damage; the kinds, the frequency and the duration of cardiac arrhythmias; and the alteration in cardiac output. Myocardial damage will be determined by six different histological or histochemical techniques, as well as by CPK isoenzyme determination. An analysis of cardiac arrhythmias will be made from continuous ECG records obtained by the Holter Monitor technique over the three-day period after the production of cerebral infarction by arterial ligation. Cardiac output will be measured periodically during experiments by the thermal dilution method. The extent and specific location of brain destruction will be determined by anatomical techniques. The neural mechanisms involved in the production of myocardial damage, cardiac arrhythmias, and altered cardiac output, which occur secondary to cerebral infarction, will be elucidated in studies utilizing the techniques of adrenalectomy, stellate ganglionectomy, vagotomy and the production of electrolytic brain lesions. The efficacy of the neuroeffector junctional blocking drugs, propranolol, practolol, and stropine in the prevention of myocardial damage, cardiac arrhythmias, and altered cardiac output, which occur secondary to cerebral infarction, will be determined, using the techniques of intra-arterial infusion at a constant rate, and periodic determinations of plasma drug concentrations during experiments. The presence or absence of sex differences in all studies will be determined.